The candidate presents a 5-year career development plan that seeks to advance the understanding of how RNA-mediated silencing signals are transported between cells, while establishing an academic career in hematopoietic stem cell transplantation (HSCT) and gene-based therapies. The candidate will build on her strong foundation in molecular genetics to gain expertise in the RNA interference (RNAi) field under the mentorship of Dr. Craig Hunter, a leader in systemic RNAi biology. In addition, the candidate will develop further clinical acumen in HSCT while participating in the establishment of a gene therapy program at Children's Hospital Boston under the guidance of Dr. David Williams. As a pioneer in the gene therapy field with extensive experience in translational research, Dr. Williams is uniquely positioned to support the proposal as a co-mentor. The plan will be conducted in the Department of Molecular and Cellular Biology at Harvard University, a founding institution of modern biology;and in the Division of Hematology/Oncology at Children's Hospital Boston, which has a distinguished record for training physician-scientists. This proposal is timely as RNAi has advanced from Nobel prize-winning discovery in 1998 to therapeutics with exceptional speed. RNAi-based therapies targeting the respiratory syncytial virus and the VEGF pathway for macular degeneration are already in clinical trials. Major barriers to successful RNAi delivery in vivo include targeting the appropriate cell type and promoting cellular uptake and release of the drug into the cytoplasm. The study of systemic RNAi in the model system Caenorhabditis elegans will provide important insights for the delivery of RNAi-based therapies in humans. For example, discovery of the widely conserved SID-1 doublestranded RNA (dsRNA) channel in C. elegans has led to strategies for enhanced delivery of dsRNA in mammalian cells. The specific aims of this proposal are: 1) to conduct a screen to identify and characterize new genes required for the spread of RNA-mediated silencing signals and 2) to analyze the role of gap junction proteins in systemic RNAi. Execution of these aims will elucidate fundamental mechanisms underlying the import and export of RNA-mediated silencing signals between cells and tissues.